Semiconductor device having thin film resistors made of bolometer materials

ABSTRACT

A semiconductor device comprising bolometers arranged in two-dimensional form corresponding to pixels for converting incoming infrared rays into electrical signals includes vertical switches, a vertical shift register, horizontal switches, and a horizontal shift register as means for selecting an arbitrary pixel. The semiconductor device is configured to allow an overcurrent to be supplied to a bolometer in a pixel selected by those means.

BACKGROUND OF THE INVENTION

[0001] (1)Field of the Invention

[0002] The present invention relates to a semiconductor device in whichthin film resistors made of bolometer materials are arranged intwo-dimensional form corresponding to pixels. The present invention alsorelates to a trimming method performed in such a semiconductor deviceand a recording medium in which a program for executing the trimming isrecorded.

[0003] (2)Description of the Prior Art

[0004] Semiconductor devices of this type include a thermal infraredimaging element, an infrared display apparatus, an ultrasonic sensor andthe like in which the use of bolometer materials as a thin film resistorconstituting part of a pixel or a sensor portion is typically known. Forexample, such devices include a thermal infrared imaging element whichconverts incident infrared rays into an electrical signal with abolometer, an infrared display apparatus which provides a desiredinfrared image by supplying a bolometer with a predetermined biasvoltage (or a bias current) to produce infrared rays (emit light), andthe like. A configuration of such a thermal infrared imaging element ishereinafter described specifically as an example of the semiconductordevice.

[0005] Each of Japanese Patent Laid-open Publication No. 8-105794 andJapanese Patent Laid-open Publication No. 9-284651 discloses a thermalinfrared imaging element comprising a plurality of thermoelectricconverting elements arranged in matrix form which absorb and convertinfrared rays radiated by respective portions of an object into heatwhich is converted into electrical signals for display as images. Apixel portion of the thermal infrared imaging element is shown in asectional view in FIG. 1 and in a plan view in FIG. 2.

[0006] Referring to FIGS. 1 and 2, there is shown semiconductorsubstrate 20 on which scanning circuit 21 comprising a switch elementand a shift register is formed, and silicon oxide film 22 partiallyincluding cavity 23 is formed on scanning circuit 21. A diaphragm (lightreceiving surface) defined by slit 26 is formed on cavity 23 in siliconoxide film 22. The diaphragm section has a three-layered configurationin which titanium bolometer 27, silicon oxide film 28, and titaniumnitride 29 are sequentially stacked on silicon oxide film 22. On siliconoxide film 22, ground line 24, signal line 25, and vertical select line30 which are made of aluminum (Al) are also formed. Signal line 25 is avertical signal line and connected to titanium bolometer 27. Titaniumbolometer 27, silicon oxide film 28, and titanium nitride 29constituting the diaphragm are infrared absorbing layers in which theinfrared rays reflected by titanium bolometer 27 is absorbed by titaniumnitride 29. A plurality of scanning circuits 21 and a plurality of thediaphragms are integrated on semiconductor substrate 20 corresponding topixels such that two-dimensional infrared images can be produced.

[0007] In the thermal infrared imaging element, when the infrared raysare incident on the diaphragm from above, the temperature of thediaphragm is changed and the electrical resistance value of titaniumbolometer 27 is changed in accordance with the change in thetemperature. The change in the resistance value of titanium bolometer 27is electrically acquired through a read circuit and read to the outsideas an infrared image.

[0008]FIG. 3 is a circuit diagram of the aforementioned thermal infraredimaging element. FIG. 4 is a timing chart for describing the operationof the thermal infrared imaging element.

[0009] As shown in FIG. 3, a pixel comprising bolometer 201 and verticalswitch 202 is connected to vertical signal line 203 and furtherconnected to horizontal switch 204. Four horizontal switches 204 areconnected to one read circuit 206, and an output from each of readcircuits 206 are sequentially provided through multiplexers 207 andoutput buffer 209 to the outside from output terminal 210. Read circuit206 can be formed of an integrating circuit, a sample hold circuit, orthe like, for example.

[0010] In the thermal infrared imaging element, as shown in FIG. 4,while an output (for example, V1) from vertical shift register 205 is at“H” level, vertical switches 202 connected thereto are turned ON and oneof four horizontal switches 204 connected to read circuit 206 is turnedON, thereby selecting a pixel. According to this configuration, onevertical period can be divided into four such that a pixel can beselected for every four pixels in the horizontal direction. The detaileddescription of the operation is described in Japanese Patent Laid-openPublication No. 8-105794 and Japanese Patent Laid-open Publication No.9-284651.

[0011] In the aforementioned conventional thermal infrared imagingelement shown in FIG. 1 and FIG. 2, since titanium bolometer 27, groundline 24, and signal line 25 are disposed on the same substrate surface,some of a pixel area is occupied by ground line 24 and signal line 25,resulting in the problem of reducing the aperture rate (fill factor) forabsorbing infrared rays.

[0012] Thus, for realizing an increased aperture rate, a thermalinfrared imaging element with a three-dimensional structure is proposedin which lines such as a ground line and a signal line electricallyconnected to a read circuit are embedded in a layer under a diaphragm.An example of a thermal infrared imaging element with such athree-dimensional structure is hereinafter described.

[0013]FIG. 5 is a plan view of a pixel in a thermal infrared imagingelement with a three-dimensional structure in which lines are embeddedin a layer under a diaphragm, and FIG. 6 is a sectional view takensubstantially along the lines X-X′ of FIG. 5. Diaphragm 4 with air gap 2disposed in a layer thereunder is supported by two beams 3 on Sisubstrate 1 provided with a read circuit. Diaphragm 4 comprises SiNinsulating protective film 5, VOx bolometer material thin film 6 formedon protective film 5, SiN insulating protective film 7 formed on thinfilm 6 through SiO insulating protective film 8. Ti wire 11 surroundedby SiN insulating protective films 5, 7 and another insulatingprotective film 9 is formed to pass through two beams 3. Bolometermaterial thin film 6 within diaphragm 4 is connected to signal line 15made of Al through Ti contact 12 and wire plug 13 made of tungsten, andsignal line 15 is electrically connected to a read circuit within Sisubstrate 1. Total reflection film 14 made of Ti is disposed on aportion of a surface of Si substrate 1 provided with a read circuit thatfaces air gap 2.

[0014] In the thermal infrared imaging element, when infrared rays 10are incident on diaphragm 4, the incident infrared rays are absorbed bySiN insulating protective film 5. Some of the infrared ray which cannotbe absorbed by SiN insulating protective film 5 is reflected by totalreflection film 14 toward diaphragm 4, and the reflected infrared raysare again absorbed by SiN insulating protective film 5. Since the lineelectrically connected to the read circuit is embedded in a layer underdiaphragm 4, a pixel area is not occupied by the wire to allow anincreased aperture rate for absorbing the infrared ray.

[0015] When the wire is embedded in the layer under the diaphragm asdescribed above, a contact is typically provided for connecting eachwire embedded in the lower layer to the bolometer in the diaphragmportion. FIG. 7 schematically shows a pixel arrangement and a positionalrelationship of contacts in a thermal infrared imaging element withwires embedded in a layer under a diaphragm. Ti contact 12A is a contactconnected to a vertical signal line, and Ti contact 12B is a contactconnected to a drain of a vertical switch constituting part of a pixel.In this configuration, the aperture rate can be further increased byreducing the size of each Ti contact and reducing a margin of theinterval (interval between Ti contact 12A and Ti contact 12B in thelower right pixel) between Ti contacts in adjacent pixels.

[0016] However, it has been found from various analysis resultspreviously made that an attempt to increase the aperture rate asdescribed above develops pixel defects due to a contact short whichcauses deteriorated image quality. For example, in the pixel arrangementshown in FIG. 7, a reduced margin of the interval between Ti contactsproduces a short in Ti contacts in adjacent pixels due to etchingresidues caused by the process, which deteriorates image quality. Theproblem of the contact short is described in detail next.

[0017] In the imaging element with the circuit configuration shown inFIG. 3, since one vertical period is divided into four such that a pixelis selected for every four pixels in the horizontal direction, more thanone switches of four horizontal switches connected to one read circuitare not selected simultaneously. If a contact short occurs, however, abias current to a bolometer also flows to an adjacent line through theshort path.

[0018]FIG. 8 is a schematic diagram showing an example of a pixelarrangement in which a contact short occurs, FIG. 9 is a schematiccircuit diagram including the contact short, and FIG. 10 is a schematicdiagram showing resistance distribution including the contact short. InFIG. 8, each contact connected to a vertical signal line is representedas “S,” and each contact connected to a drain of a vertical switch isrepresented as “D.” FIG. 8 shows a state where a short occurs in Scontact at row b and column 2 (hereinafter represented as [b,2]) and Dcontact at [c,3]. FIG. 9 illustrates the contact short shown in FIG. 8in a circuit diagram, and FIG. 10 shows distribution of resistances ofbolometers when the short path shown in FIG. 8 is produced. FIGS. 11a to11 c schematically show paths for flowing bias currents when the contactshort shown in FIGS. 8 to 10 occurs. FIG. 11a shows a path for flowing abias current when pixel [a,2] in FIG. 10 is selected, from which it canbe seen that a bolometer resistance value is 2R/3. FIG. 11b shows a pathfor flowing a bias current when pixel [c,2] in FIG. 10 is selected, fromwhich it can be seen that a short occurs. FIG. 11c shows a path forflowing a bias current when pixel [c,3] in FIG. 10 is selected, fromwhich it can be seen that a bolometer resistance value is R.

[0019] In the thermal infrared imaging element, typically, variations inbolometer resistance values (unevenness) limit the dynamic range of theread circuit and produce variations in sensitivity of the imagingelement. Thus, smaller variations (unevenness) are preferable in thebolometer resistance values. Evaluations in previously published papersshow that variations (unevenness) in the bolometer resistance values aretypically approximately 10% p-p with respect to the central resistancevalue, and a pixel with a resistance value above the range is adefective pixel. In the aforementioned three-dimensional configuration,assuming that the bolometer resistance value is R, the bolometerresistance value appears to be 2R/3 in two lines in the verticaldirection where a contact short occurs, as shown in FIG. 10. Thiscorresponds to −33% if converted into variations in resistance(unevenness), and the pixels with the two lines serve as defectivepixels.

[0020] In this manner, a contact short at one point affects two lines inthe vertical direction. For example, in an array of 320 by 240 inhorizontal and vertical directions, respectively, if a contact shortoccurs at one point, the number of defects amounts to 480 pixelsmultiplied by 2 lines by 240 pixels, representing a deteriorated pixeldefective rate. In addition, defective pixels due to such a contactshort are produced regularly in two lines in the vertical direction, andare extremely prominent as linear flaws when imaging is performed,resulting in significantly deteriorated good item yields.

[0021] From the aforementioned reasons, in the imaging element with thethree-dimensional configuration, a serious problem is how to eliminatedeteriorated image quality due to a contact short for increasing theaperture rate. In addition, the problem of the deteriorated imagequality due to a contact short described above occurs not only in thethermal infrared imaging element but also in general semiconductordevices including the aforementioned infrared display, ultrasonic sensorand the like.

SUMMARY OF THE INVENTION

[0022] It is an object of the present invention to provide asemiconductor device and a trimming method which can reduce the effectof defective pixels caused by the aforementioned contact short. It isanother object of the present invention to provide a recording mediumwhich records a program for executing the trimming.

[0023] To achieve the aforementioned objects, the semiconductor deviceof the present invention comprises thin film resistors arranged intwo-dimensional form corresponding to pixels for converting incominginfrared rays into electrical signals or for emitting infrared rays, andselecting means for selecting an arbitrary thin film resistor to supplyan overcurrent to the selected thin film resist.

[0024] The semiconductor device of the present invention comprises thinfilm resistors arranged in two-dimensional form corresponding to pixelsfor converting incoming infrared rays into electrical signals or foremitting infrared rays, wherein the thin film resistors are connected toa vertical signal line for each column and each of the thin filmresistors is provided with a semiconductor switch, each of the pixelsincludes a first contact connected to the vertical signal line and asecond contact connected to a drain of the semiconductor switch, and thefirst contact is disposed close to the second contact in adjacent pixelsin the column direction.

[0025] The semiconductor device of the present invention comprises thinfilm resistors arranged in two-dimensional form corresponding to pixelsfor converting incoming infrared rays into electrical signals or foremitting infrared rays, wherein the thin film resistors are connected toa vertical signal line for each column and each of the thin filmresistors is provided with a semiconductor switch, each of the pixelsincludes a first contact connected to the vertical signal line and asecond contact connected to a drain of the semiconductor switch, andeither the first contacts or the second contacts are disposed close toeach other in adjacent pixels in the column direction. In this case, thefirst contact may be used in common for adjacent pixels in the columndirection.

[0026] The trimming method of the present invention for a semiconductordevice comprising thin film resistors arranged in two-dimensional formcorresponding to pixels for converting incoming infrared rays intoelectrical signals or for emitting infrared rays comprises the step offlowing an overcurrent to desired thin film resistors.

[0027] The recording medium of the present invention records a programfor causing a computer to execute the processing of:

[0028] sequentially selecting pixels in a semiconductor devicecomprising thin film resistors arranged in two-dimensional formcorresponding to pixels for converting incoming infrared rays intoelectrical signals or for emitting infrared rays;

[0029] measuring resistance values of the thin film resistors of theselected pixels;

[0030] detecting a pixel with a resistance value deviating from apredefined value based on the measuring results; and

[0031] flowing an overcurrent to a thin film resistor in a predeterminedpixel adjacent to the detected pixel.

[0032] In the present invention as described above, the followingeffects are provided.

[0033] As described in the aforementioned problem, when a contact shortoccurs in a pixel to be supplied with a bias current and a pixeladjacent thereto, the bias current also flows to an adjacent linethrough the short path to cause defective pixels in two lines in thevertical direction where the contact short occurs. According to thepresent invention, an overcurrent is supplied to a thin film resistor(bolometer) in the adjacent pixel where the contact short occurs. Thethin film resistor (bolometer) supplied with the overcurrent is burnt byexcessive self-heating, resulting in the elimination of the short path.

[0034] In an aspect of the present invention in which the first contactis disposed close to the second contact in adjacent pixels in the columndirection, even when a contact short occurs, only the resistance valuein the pixel including the second contact represents a short state andthe effect is not produced on two lines in the vertical direction.

[0035] In an aspect of the present invention in which either firstcontacts or second contacts are disposed close to each other in adjacentpixels in the column direction, when a short occurs in the secondcontacts, its effect is produced only in the two pixels where thecontact short occurs and the effect is not caused on two lines in thevertical direction. On the other hand, when a short occurs in the firstcontacts, the contact short causes no effect since they are connected tothe same vertical signal line. In this configuration, in an aspect inwhich one of the contacts is used in common for adjacent pixels, theaperture rate and integration degree are further increased since wiringis also used in common.

[0036] The above and other objects, features, and advantages of thepresent invention will become apparent from the following descriptionwith reference to the accompanying drawings which illustrate examples ofthe present invention.

BRIEF DESCRIPTION OF THE DRAWINGS

[0037] In the accompanying drawings:

[0038]FIG. 1 is a sectional view of a pixel of a conventional thermalinfrared imaging element;

[0039]FIG. 2 is a plan view of the pixel of the conventional thermalinfrared imaging element;

[0040]FIG. 3 is a circuit diagram of the conventional thermal infraredimaging element;

[0041]FIG. 4 is a timing chart for describing the operation of thethermal infrared imaging element shown in FIG. 3;

[0042]FIG. 5 is a plan view showing an example of a pixel of a thermalinfrared imaging element with a three-dimensional configuration in whichwires are embedded in a layer under a diaphragm;

[0043]FIG. 6 is a sectional view taken along X-X′ in the pixel shown inFIG. 5;

[0044]FIG. 7 is a schematic diagram showing an example of a pixelarrangement and a positional relationship of contacts in a thermalinfrared imaging element in which wires are embedded in a layer under adiaphragm;

[0045]FIG. 8 is a schematic diagram showing the pixel arrangement in thethermal infrared imaging element shown in FIG. 7;

[0046]FIG. 9 is a schematic circuit diagram showing the thermal infraredimaging element shown in FIG. 7;

[0047]FIG. 10 is a schematic diagram showing resistance distribution inthe thermal infrared imaging element shown in FIG. 7;

[0048]FIG. 11(a) is a schematic circuit diagram showing in detail a pathfor flowing a bias current when pixel [a,2] in FIG. 10 is selected;

[0049]FIG. 11(b) is a schematic circuit diagram showing in detail a pathfor flowing a bias current when pixel [c,2] in FIG. 10 is selected;

[0050]FIG. 11(c) is a schematic circuit diagram showing in detail a pathfor flowing a bias current when pixel [c,3] in FIG. 10 is selected;

[0051]FIG. 12 is a circuit diagram showing a thermal infrared imagingelement which is a first embodiment of a semiconductor device of thepresent invention;

[0052]FIG. 13 is a schematic circuit diagram for describing trimming forthe contact short shown in FIG. 8 to FIG. 10;

[0053]FIG. 14 is a schematic diagram showing resistance distributionafter the trimming shown in FIG. 13;

[0054]FIG. 15 is a flow chart for good item selection which employs thetrimming method of the present invention;

[0055]FIG. 16 is a block diagram showing an example of a trimmingsystem;

[0056]FIG. 17 is a schematic diagram showing a pixel arrangement in athermal infrared imaging element which is a second embodiment of thesemiconductor device of the present invention;

[0057]FIG. 18 is a schematic circuit diagram of the thermal infraredimaging element which is the second embodiment of the semiconductordevice of the present invention;

[0058]FIG. 19 is a schematic diagram showing resistance distribution inthe circuit shown in FIG. 18;

[0059]FIG. 20 is a schematic diagram showing a pixel arrangement in athermal infrared imaging element which is a third embodiment of thesemiconductor device of the present invention;

[0060]FIG. 21 is a schematic circuit diagram of the thermal infraredimaging element which is the third embodiment of the semiconductordevice of the present invention;

[0061]FIG. 22 is a schematic diagram showing resistance distribution inthe circuit shown in FIG. 21;

[0062]FIG. 23 is a diagram showing an example of a wiring pattern of avertical signal line in the circuit shown in FIG. 21;

[0063]FIG. 24 is a schematic diagram showing a pixel arrangement in athermal infrared imaging element which is a fourth embodiment of thesemiconductor device of the present invention;

[0064]FIG. 25 is a circuit diagram showing an example of a configurationof an infrared display element which is a fifth embodiment of thesemiconductor device of the present invention; and

[0065]FIG. 26 is a diagram showing an example of a configuration of aninfrared display apparatus using the infrared display element shown inFIG. 25.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0066] Next, embodiments of the present invention are described withreference to the drawings.

[0067] A semiconductor device of the present invention includes thinfilm resistors made of bolometer materials arranged in two-dimensionalform corresponding to respective pixels, and represents athree-dimensional configuration as shown in FIGS. 5 and 6 mentionedabove. The configuration and operation of the semiconductor device ofthe present invention are specifically described hereinafter with athermal infrared imaging element and an infrared display element asexamples.

[0068] (Embodiment 1: Thermal Infrared Imaging Element)

[0069]FIG. 12 is a circuit diagram of a thermal infrared imaging elementwhich is a first embodiment of the semiconductor device of the presentinvention. In the thermal infrared imaging element, bolometer 101 andvertical switch 102 constitute a pixel. Each pixel is configured asshown in FIGS. 5 and 6 mentioned above, and converts the incidentinfrared rays into heat. As a pixel arrangement, various pixelarrangements are applicable in addition to the pixel arrangement shownin FIG. 7 mentioned above.

[0070] Bolometer 101 is connected to vertical signal line 103 andfurther to horizontal switch 104. Horizontal switch 104 is selected withcontrol pulses φHA to φHD. Four horizontal switches 104 are connected toone read circuit 106 such that outputs from read circuits 106 aresequentially provided to the outside through multiplexers 107 and outputbuffer 109. Read circuit 106 can be formed of an integrating circuit, asample hold circuit or the like. A pixel is selected in timing such thatwhile an output (for example, V1) from vertical shift register 105 is at“H” level, vertical switches 102 connected thereto are turned ON and oneof four horizontal switches 104 connected to read circuit 106 is turnedON. With this pixel selection, one vertical period is divided into fourand a pixel is selected every four pixels in the horizontal direction.

[0071] In the aforementioned configuration, when the size of eachcontact is reduced and each interval margin between contacts in adjacentpixels is reduced for increasing the aperture rate, a contact shortoccurs in adjacent pixels as described above. When such a contact shortoccurs in adjacent pixels, a bias current to a bolometer also flows toan adjacent line through the short path to cause the bolometerresistance value to appear to be 2R/3 in two lines in the verticaldirection where the contact short occurs, resulting in defective pixels(see FIGS. 8 to 10). The defective pixels can be restored by burning theadjacent pixel in which the contact short occurs.

[0072] Thus, in the configuration shown in FIG. 12, each vertical signalline 103 is connected to horizontal shift register 112 through eachhorizontal switch 111 such that an arbitrary single pixel can bedirectly accessed with φHINB which is a data input signal for horizontalshift register 112 and φHCLK which is a clock signal. This configurationenables selection of a desired pixel and a predetermined amount ofcurrent to flow to a bolometer of the selected defective pixel. Thecurrent is supplied to the bolometer of the selected pixel by anexternal power circuit connected to Rout 113.

[0073] When horizontal switch 111 is used, horizontal switch 104 isturned OFF to hold read circuit 106 in a disconnected state. Incontrast, when horizontal switch 104 is used to produce an output fromread circuit 106 to the outside, horizontal switch 111 is held in adisconnected state.

[0074] Next, description is made for a trimming technique for restoringa defective pixel caused by a contact short in adjacent pixels. FIG. 13is a schematic circuit diagram illustrating an example of a contactshort. FIG. 14 is a schematic diagram showing resistance distributionafter the trimming.

[0075] A bolometer can be typically burnt down itself by flowing anovercurrent in a vacuum to cause excessive self-heating of thebolometer. Actually, beams for supporting a diaphragm may be burnt andbroken. Assuming that the temperature(approximately several hundreds ofdegrees centigrade actually) at which a bolometer is burnt withself-heating is T (° C.), applied voltage VD (V) can be represented asfollows:

VD=(T×R×Gth)^(1/2)

[0076] where R (Ω) represents a bolometer resistance value, and Gth(W/K) represents a heat conductance in a vacuum.

[0077] If T=500° C., R=10 k Ω, and Gth=0.2 μW/K, then VD=1V.

[0078] Referring to FIG. 11a mentioned above for description, theresistance value is 2R/3 in the two lines in the vertical directionwhere the contact short occurs because a bias current flows to the 3rdline of the vertical signal lines through the bolometer at [c,3] fromthe short path. In this case, vertical shift register 105, horizontalswitch 111 and horizontal shift register 112 are used to select thepixel on the right of the shorted pixel, i.e. the pixel including thecontact connected to the drain of vertical switch 102 (the pixelimmediately to the right of the shorted pixel in the resistancedistribution in FIG. 10) for burning down the bolometer itself byflowing an overcurrent in a vacuum through Rout 113 (see FIG. 13),thereby making it possible to eliminate the current path caused by thecontact short. This allows the resistance value which appeared to be2R/3 in the lines in the vertical direction to be restored to a truebolometer resistance value R (see FIG. 14), and the effect on the linesin the vertical direction can be removed.

[0079] When a contact short is physically minor, a short path itself canbe burnt down by flowing a current through the short path. In this case,the effect on lines in the vertical direction can also be removedsimilarly to the aforementioned case.

[0080] When the state of a contact short is not an obvious short butrepresents connection, for example at several megohms, a bolometerresistance value shows no anomaly since the effect on vertical linescorresponds to almost leak current (sub-μ A). In this case, the effecton lines in the vertical direction is observed as vibration noise.However, if pixel [c,3] is selected as shown in FIG. 9, the effect of aleak path is reduced and the action of vibration noise is not observed.In such a case, the point of the contact short can be specified bysearching two vertical lines for a target pixel. The specified contactshort point is then subjected to the aforementioned trimming to allowthe effect on lines in the vertical direction to be eliminatedsimilarly.

[0081] The trimming technique described above is particularly effectivein the following process. Specifically, in the process of measuringbolometer resistance values of all pixels in a thermal infrared imagingelement with a fully automatic wafer prober or the like to select aquality item based on the resistance values, when bolometer resistancevalues represent 2R/3 in two lines in the vertical direction, the twolines are automatically searched for a pixel immediately to the right ofa shorted pixel, and its bolometer itself is burnt down by usingexcessive self-heating. This enables elimination of defects in the twolines due to a contact short as well as improvements in quality itemyields and productivity.

[0082] As an example, FIG. 15 shows a flow chart for selecting qualityitems which employs the aforementioned trimming technique. In thequality item selection, first at step S10, bolometer resistance valuesare measured for all pixels of a chip. Next at step S11, a check is madeto determine if a bolometer resistance value represents 2R/3 in twolines in the vertical direction. If a bolometer resistance value of 2R/3is present, first, the two lines in the vertical direction are searchedfor a shorted pixel at step S12. At step S13, the pixel immediately tothe right of the shorted pixel searched for is selected, and anovercurrent is flown to burn down the bolometer in the pixel at stepS14. Then, the processing is moved to measurement of the next chip atstep S15, and returns to the aforementioned step S10. If there is nobolometer value of 2R/3, the processing is moved directly to step S15.

[0083]FIG. 16 shows an example of a system for performing theaforementioned trimming. In FIG. 16, thermal infrared imaging element1001 is the thermal infrared imaging element shown in FIG. 12 mentionedabove, and comprises pixel portion 1002 in which bolometers forconverting incident infrared rays into electrical signals are arrangedin two-dimensional form corresponding to pixels, and access circuit 1003for directly accessing an arbitrary single pixel in pixel portion 1002.Access circuit 1003 is formed of a shift register, a decoder and thelike, and comprises vertical shift register 105, horizontal switches111, horizontal shift register 112 and the like shown in FIG. 12.

[0084] A pixel selected by access circuit 1003 is connected toresistance value measuring circuit 1006 and voltage supply unit 1008through signal line 1004. RAM (Random Access Memory) 1007 is providedfor storing the measurement results in resistance value measuringcircuit 1006. Recording medium 1009 comprises a magnetic disc, asemiconductor memory or other various types of recording media, andpreviously records a program which can execute the trimming procedurefrom steps S10 to S15 shown in FIG. 15. CPU 1005 executes trimmingprocessing as described below in accordance with the program recorded inrecording medium 1009.

[0085] First, CPU 1005 controls access circuit 1003 to sequentiallyselect pixels in pixel portion 1002 of thermal infrared imaging element1001, controls resistance value measuring circuit 1006 to measure theresistance values of the selected pixels, and causes the measurementresults to be stored in RAM (Random Access Memory) 1007.

[0086] After the resistance values of all pixels of pixel section 1002are measured and the results are stored in RAM 1007, CPU 1005 reads themeasurement results stored in RAM 1007 to search whether any pixel has aresistance value deviating from a predefined value. If any pixel has aresistance value deviating from the predefined value, CPU 1005 controlsaccess circuit 1003 to select the pixel immediately to the right of thepixel and controls voltage supply unit 1008 to apply a predeterminedvoltage to the selected pixel. This causes an overcurrent to flowthrough the bolometer of the pixel on the right of the pixel with theresistance value deviating from the predefined value, thereby burningdown the bolometer.

[0087] In the aforementioned trimming system, as means for burning abolometer, means for use in typical trimming such as means using a laseror an electrical beam can be applied in addition to the aforementionedmeans using voltage.

[0088] (Embodiment 2: Thermal Infrared Imaging Element)

[0089]FIG. 17 is a schematic diagram showing a pixel arrangement in athermal infrared imaging element which is a second embodiment of thesemiconductor device of the present invention.

[0090] The thermal infrared imaging element of the embodiment has aconfiguration similar to that of the aforementioned first embodimentexcept for the pixel arrangement. Since the first embodiment employs thepixel arrangement shown in FIGS. 7 and 8, the occurrence of a contactshort means a short in a vertical signal line and a drain of a verticalswitch over two adjacent lines as shown in FIG. 9 to represent adefective mode in which a bolometer resistance value is 2R/3 in twolines in the vertical direction. In contrast, the embodiment isconfigured to eliminate such a defective mode by changing the pixelarrangement.

[0091] The thermal infrared imaging element of the embodiment has aconfiguration in which the pixel arrangement is symmetrical with respectto the X axis for each line as shown in FIG. 17. Thus, close contacts inadjacent pixels in the column direction are contacts connected to avertical signal line, or contacts connected to drains of verticalswitches. FIG. 17 shows a short of contacts for [a,3] and [b,3]connected to a vertical signal line, and a short of contacts for [b,2]and [c,2] connected to drains of vertical switches.

[0092]FIG. 18 is a schematic circuit diagram of the thermal infraredimaging element of the embodiment, and FIG. 19 is a schematic diagramshowing resistance distribution thereof. FIG. 18 illustrates the contactshorts shown in FIG. 17 in a circuit diagram, and FIG. 19 showsresistance distribution of bolometers when short paths shown in FIG. 18are produced.

[0093] In the thermal infrared imaging element of the embodiment, when ashort occurs in the contacts for [a,3] and [b,3] connected to thevertical signal line, no effect is present since they are connected tothe same vertical signal line as shown in FIGS. 18 and 19. On the otherhand, when a short occurs in the contacts for [b,2] and [c,2] connectedto the drains of the vertical switches, if [b,2] is selected, a biascurrent flows from the vertical switch for [b,2] to the ground throughboth bolometers for [b,2] and [c,2], and the resistance values of thebolometers in the pixels appear to be R/2. If [c,2] is selected, theresistance values also appear to be R/2.

[0094] While the aforementioned first embodiment presents the effect ofa contact short at one point on two lines in the vertical direction, inthe second embodiment, the effect of a contact short is seen only when ashort occurs in contacts connected to drains of vertical switches. Thus,the occurrence rate becomes ½. In addition, in the second embodiment,the resistance values of two pixels where a contact short occurs areR/2, but the effect is not produced on two lines in the verticaldirection.

[0095] In the aforementioned manner, the thermal infrared imagingelement of the embodiment can suppress the effect of a contact shortwithout performing the trimming described in the first embodiment.

[0096] It should be noted that since the circuit configuration of thethermal infrared imaging element of the embodiment is similar to theconfiguration of the imaging element shown in FIG. 3 mentioned above, adetailed description thereof is omitted.

[0097] (Embodiment 3: Thermal Infrared Imaging Element)

[0098]FIG. 20 is a schematic diagram showing a pixel arrangement of athermal infrared imaging element which is a third embodiment of thesemiconductor device of the present invention.

[0099] The thermal infrared imaging element of the embodiment also has aconfiguration similar to that of the aforementioned first embodimentexcept for the pixel arrangement. FIG. 20 shows a state where a shortoccurs in a contact for [b,3] connected to a vertical signal line and acontact for [c,3] connected to a drain of a vertical switch.

[0100] Since the pixel arrangement shown in FIG. 20 is symmetrical withrespect to the Y axis for each line, each S contact connected to avertical signal line is disposed close to each D contact connected to adrain of a vertical switch in adjacent pixels in the column direction.

[0101]FIG. 21 is a schematic circuit diagram of the thermal infraredimaging element of the embodiment, and FIG. 22 is a schematic diagramshowing resistance distribution thereof. FIG. 21 illustrates the contactshort shown in FIG. 20 in a circuit diagram, and FIG. 22 showsresistance distribution of bolometers when a short path shown in FIG. 21is produced.

[0102] In the thermal infrared imaging element of the embodiment, when acontact short occurs, the resistance value of a pixel including acontact connected to a drain of a vertical switch represents a shortstate, but its effect is not produced on two lines in the verticaldirection, as shown in FIGS. 21 and 22. Thus, the embodiment can alsosuppress the effect of a contact short without performing the trimmingdescribed in the aforementioned first embodiment.

[0103] The circuit configuration of the thermal infrared imaging elementof the embodiment is similar to the configuration of the imaging elementshown in FIG. 3 mentioned above; therefore, a detailed descriptionthereof is omitted.

[0104] In the case of the pixel arrangement of the thermal infraredimaging element of the embodiment, a turned wiring pattern is providedfor the vertical signal line as shown in FIG. 23. In contrast, in thearrangement of the aforementioned second embodiment, since the contactsconnected to the vertical signal line are linearly arranged as shown inFIG. 17, a simple linear wiring pattern can be provided. Thus, it can besaid that the pixel arrangement shown in the second embodiment is morepreferable in consideration of the wiring pattern.

[0105] (Embodiment 4: Thermal Infrared Imaging Element)

[0106]FIG. 24 is a schematic diagram showing a pixel arrangement of athermal infrared imaging element which is a fourth embodiment of thesemiconductor device of the present invention.

[0107] The thermal infrared imaging element of the embodiment also has aconfiguration similar to that of the aforementioned first embodimentexcept for the pixel arrangement. Since the pixel arrangement issymmetrical with respect to the X axis for each line as shown in FIG.24, close contacts in adjacent pixels in the column direction arecontacts connected to a vertical signal line in two pixels in thevertical direction, or contacts connected to drains of verticalswitches. Since contacts in two pixels in the vertical direction areconnected to a common vertical signal line, a contact can be used incommon therefor. In an example shown in FIG. 24, a contact (representedas “S” in FIG. 24) connected to a vertical signal line is used in commonfor two pixels. This enables improvements in the aperture rate andperformance.

[0108] The circuit configuration of the thermal infrared imaging elementof the embodiment is also similar to the configuration of the imagingelement shown in FIG. 3 mentioned above; therefore, a detaileddescription thereof is omitted.

[0109] (Embodiment 5: Infrared Display Element)

[0110]FIG. 25 is a circuit diagram showing an example of a configurationof an infrared display element which is a fifth embodiment of thesemiconductor device of the present invention.

[0111] In FIG. 25, each of resistors 2001 is a thin film resistor formedof a bolometer, a piezoresistor or the like, and resistors 2001 arearranged in two-dimensional form corresponding to pixels. Each resistor2001 is connected to vertical shift register 2004 through verticalswitch 2002 and to a vertical signal line for each column, and eachvertical signal line is connected to horizontal shift register 2005through horizontal switch 2003. Each vertical signal line can beprovided with a bias current or a bias voltage from signal line 2006through horizontal switch 2003.

[0112] In the infrared display element, vertical shift register 2004 andhorizontal shift register 2005 are driven by an external drivingcircuit, pixels are sequentially selected with vertical switches 2002and horizontal switches 2003, and resistor 2001 of the selected pixel isprovided with a predetermined amount of bias current or bias voltagefrom signal line 2006. Resistor 2001 supplied with the predeterminedamount of bias current or bias voltage outputs infrared rays (emitslight) in accordance with the bias current or bias voltage.

[0113] The infrared display element of the embodiment employs theaforementioned three-dimensional configuration (see FIGS. 5 and 6) forthe purpose of achieving high-density integration. Thus, the problem ofa contact short occurs similarly to the aforementioned thermal infraredimaging element. For solving the problem of the contact short, theinfrared display element of the embodiment can take forms similar to thethermal infrared imaging elements of the aforementioned first to fourthembodiments.

[0114] When the infrared display element of the embodiment employs theform of the thermal infrared imaging element of the aforementioned firstembodiment, vertical switch 2002 and horizontal switch 2003 are used toselect the pixel immediately to the right of a pixel where a shortoccurs, i.e. the pixel including a contact connected to a drain ofvertical switch 2002, resistor 2001 (bolometer in this case) of theselected pixel is supplied with an overcurrent through signal line 2006in a vacuum to burn the bolometer itself (trimming processing). Thisprocessing can eliminate a current path caused by the contact short andremove the effect on lines in the vertical direction (specifically, theresistance values of two lines in the vertical direction appearing to be2R/3 due to the contact short).

[0115] The trimming processing procedure in the infrared display elementof the embodiment is performed similarly to the case of the thermalinfrared imaging element of the aforementioned first embodiment, and asystem with a similar configuration to the first embodiment isapplicable.

[0116] When the infrared display element of the embodiment employs theforms of the thermal infrared imaging elements of the aforementionedsecond to fourth embodiments, similar configurations are used. Thedetailed description thereof is thus omitted.

[0117]FIG. 26 shows an example of an infrared display apparatus usingthe infrared display element of the embodiment. In FIG. 26, infrareddisplay element 3001 is the infrared display element shown in FIG. 25,and driven by a driving circuit, not shown. In the infrared displayapparatus, an infrared ray output from infrared display element 3001 areradiated to infrared display 3003 through lens 3002, thereby displayingan image on infrared display 3003.

[0118] The aforementioned system shown in FIG. 16 is applicable as asystem for performing trimming in the infrared display element of theembodiment. In this case, in the configuration shown in FIG. 16, thermalinfrared imaging element 1001 is replaced with the infrared displayelement of the embodiment in which pixel portion 1002 is configured suchthat bolometers emitting infrared rays are arranged in two-dimensionalform corresponding to pixels, and access circuit 1003 comprises verticalswitches 2002, vertical shift register 2004, horizontal switches 2003,and horizontal shift register 2005. CPU 1005 performs similar trimmingprocessing in which respective pixels are sequentially selected, theresistance values of the selected pixels are measured, a pixel with aresistance value deviating from a predefined value is detected based onthe measurement results, and an overcurrent is provided to a thin filmresistor in a predetermined pixel adjacent to the detected pixel.

[0119] While the thermal infrared imaging element and the infrareddisplay element have been described as the embodiments of thesemiconductor device of the present invention, the present invention isnot limited to these elements. For example, the trimming is applicableto any semiconductor device in which thin film resistors burnable by anovercurrent are arranged in two-dimensional form corresponding topixels. In addition, the pixel arrangement is applicable to anysemiconductor device with the aforementioned three-dimensionalconfiguration in which thin film resistors are arranged intwo-dimensional form corresponding to pixels.

[0120] According to the present invention configured as described above,when a contact short occurs, its short path can be eliminated to removethe effect of the contact short on lines in the vertical direction,thereby making it possible to improve yields in manufacturing steps. Inaddition, it is possible to improve the aperture rate in a thermalinfrared imaging element and high-density integration in an infrareddisplay element.

[0121] When contacts connected to drains of vertical switches areclosely disposed, a short of contacts connected to a vertical signalline produces no effect. Thus, the effect of a contact short can bereduced accordingly.

[0122] Additionally, when a contact connected to a vertical signal lineis used in common for two pixels in the vertical direction, furtherimprovements can be provided in the aperture rate and performance.

[0123] Furthermore, when a contact connected to a vertical signal lineis disposed close to a contact connected to a drain of a vertical switchin adjacent pixels in the column direction, a short state, even whenrepresented by the resistance value of the pixel including the contactconnected to the drain of the vertical switch, causes no effect on twolines in the vertical direction. Thus, the effect of a contact short canbe reduced.

[0124] While preferred embodiments of the present invention have beendescribed using specific terms, such description is for illustrativepurposes only, and it is to be understood that changes and variationsmay be made without departing from the spirit or scope of the followingclaims.

1. A semiconductor device comprising: thin film resistors arranged intwo-dimensional form corresponding to pixels for converting incominginfrared rays into electrical signals or for emitting infrared rays; andselecting means for selecting an arbitrary thin film resistor from saidthin film resistors to supply an overcurrent to the selected thin filmresistor.
 2. A semiconductor device according to claim 1, wherein saidselecting means includes: a first semiconductor switch provided to eachof the thin film resistors; a first shift register connected to each ofthe thin film resistors through the first semiconductor switch; aplurality of vertical signal lines to which the thin film transistors isconnected for each column; a second semiconductor switch provided toeach of the vertical signal lines; a second shift register connected toeach of the vertical signal lines through the second semiconductorswitch.
 3. A semiconductor device according to claim 2, furthercomprising: a third shift register for reading an electrical signalconverted by the thin film resistor in each of the pixels, and whereinelectrical signals converted by the thin film resistors in the pixels,which is sequentially selected by the first and third shift registers,is output to the outside.
 4. A semiconductor device according to claim2, wherein a predetermined amount of voltage or current is supplied tothe thin film resistor selected by the first and second shift registers.5. A semiconductor device comprising: thin film resistors arranged intwo-dimensional form corresponding to pixels for converting incominginfrared rays into electrical signals or for emitting infrared rays; asemiconductor switch provided to each of the thin film resistors; asignal line to which the thin film transistors is connected for eachcolumn; a first contact connected to the vertical signal line; and asecond contact connected to a drain of the semiconductor switch; whereinthe first contact is disposed close to said second contact in adjacentpixels in the column direction.
 6. A semiconductor device comprising:thin film resistors arranged in two-dimensional form corresponding topixels for converting incoming infrared rays into electrical signals orfor emitting infrared rays; a semiconductor switch provided to each ofthe thin film resistors; a signal line to which the thin filmtransistors is connected for each column; a first contact connected tothe vertical signal line; and a second contact connected to a drain ofthe semiconductor switch; wherein either the first contacts or thesecond contacts are disposed close to each other in adjacent pixels inthe column direction.
 7. A semiconductor device according to claim 6,wherein said first contact is used in common for adjacent pixels in thecolumn direction.
 8. A semiconductor device according to claim 1,wherein the thin film resistor is formed of a bolometer material.
 9. Asemiconductor device according to claim 5, wherein the thin filmresistor is formed of a bolometer material.
 10. A semiconductor deviceaccording to claim 6, wherein the thin film resistor is formed of abolometer material.
 11. A method of trimming for a semiconductor devicecomprising thin film resistors arranged in two-dimensional formcorresponding to pixels for converting incoming infrared rays intoelectrical signals or for emitting infrared rays, comprising the step offlowing an overcurrent to a desired one of said thin film resistors. 12.A method of trimming according to claim 11, further comprising the stepsof: measuring a resistance value of the thin film resistor for each ofsaid pixels; detecting a pixel with a resistance value deviated from apredefined value; and supplying an overcurrent to a thin film resistorin a predetermind pixel adjacent to the detected pixel.
 13. A method oftrimming according to claim 12, wherein said pixel adjacent to thedetected pixel is a pixel provided with a semiconductor switch includinga drain disposed at the closest position to a vertical signal lineconnected to a thin film resistor of said detected pixel.
 14. Arecording medium for recording a program for causing a computer toexecute the processing of: sequentially selecting pixels in asemiconductor device in which thin film resistors for convertingincoming infrared rays into electrical signals or for emitting infraredrays are arranged in two-dimensional form corresponding to the pixels;measuring resistance values of the thin film resistors of said selectedpixels; detecting a pixel with a resistance value deviating from apredefined value based on the measuring results; and flowing anovercurrent to a thin film resistor in a predetermined pixel adjacent tosaid detected pixel.